FGSM [1]} is designed to produce an adversarial signal in a fast, non-iterative manner. It computes the gradient of the cost function \(J\)  w.r.t input \(\operatornamewithlimits{\mathbf {x}}\)  and scales the sign of the gradient by a \({L_{\infty }}\)  constraint for generating \(\delta _{\operatornamewithlimits{\mathbf {x}}}\) :
\(\mathbf {x}^* = \operatornamewithlimits{\mathbf {x}}+ {\varepsilon }{\cdot }sign\left({\nabla }_{x}J\left(\theta ,\operatornamewithlimits{\mathbf {x}},y \right)\right),\) 
